1. Field Of The Invention
This invention relates to apparatus for providing oxygen enriched air through the use of permeable films or membranes, and more particularly, to such apparatus which increases or regulates the temperature and humidity of the oxygen-enriched air being delivered to a patient, and is an improvement over prior U.S. Pat. No. 4,174,955.
2. Prior Art
As is known, various types of equipment have been used to supply aged or infirm patients with oxygen or oxygen-enriched air in order to sustain life-support systems or relieve symptoms of various types of debilitating diseases, particularly of the lungs. In some cases, use has been made of pure oxygen or oxygen-enriched gases supplied from pressurized cylinders. However, such cylinders are cumbersome and have relatively short useful life.
In other cases, use has been made of machines for enriching the amount of oxygen in the air supplied to a patient. For example, as described in U.S. Pat. No. 3,976,451, use has been made of a vacuum extract machine for in-home use, under a doctor's supervision, by patients suffering respiratory ailments and requiring oxygen-enriched air. Generally, this type of machine employs a membrane oxygen enricher and does not require the storing of large volumes of oxygen under pressure. Instead, the machine operates so as to pass a continuous flow of air through permeable membrane cells which permeate oxygen more readily than nitrogen and to draw off air enriched with oxygen from the cells. The machine also employs additional apparatus to control the temperature of the atmospheric air directed to the membrane cells, in particular, a sliding valve plate arrangement which directs or diverts preheated air to the cells.
However, the arrangement of components of a machine as described in U.S. Pat. No. 3,976,451 requires a relatively large amount of space. Further, the machine has been relatively noisy in operating, for example, at a sound level detrimental to a device for in-home operation, typically about 52 dbA.
In addition, the machine employs a condenser to remove excess water vapor from the oxygen-enriched air after cooling. This excess water is usually collected in a vessel that is emptied in response to a float valve. However, such a float valve is prone to both leakage and sticking because of corrosion and wear particles in the water flow. Further, the float valve requires a large resident volume of water to operate. Such a resident volume is, however, subject to freezing and bacterial contamination.
The invention disclosed in our prior patent, U.S. Pat. No. 4,174,955, solves the problems above with respect to other prior art devices. However, it has been noted that the relatively cool temperature of the oxygen-enriched air being delivered to the patient may result in discomfort to the patient after a length of time has passed. Moreover, the relatively low absolute humidity of the air being delivered can result in respiratory irritation.